Herschel observed Stripe 82 quasars and their host galaxies: connections between the AGN activity and the host galaxy star formation

Abstract

In this work, we present a study of 207 quasars selected from the Sloan Digital Sky Survey quasar catalogs and the Herschel Stripe 82 survey. Quasars within this sample are high luminosity quasars with a mean bolometric luminosity of $10^{46.4}$ erg s$^{-1}$. The redshift range of this sample is within $z<4$, with a mean value of $1.5\pm0.78$. Because we only selected quasars that have been detected in all three Herschel-SPIRE bands, the quasar sample is complete yet highly biased. Based on the multi-wavelength photometric observation data, we conducted a spectral energy distribution (SED) fitting through UV to FIR. Parameters such as active galactic nucleus (AGN) luminosity, FIR luminosity, stellar mass, as well as many other AGN and galaxy properties are deduced from the SED fitting results. The mean star formation rate (SFR) of the sample is 419 $M_{\odot}$ yr$^{-1}$ and the mean gas mass is $\sim 10^{11.3}$ $M_{\odot}$. All these results point to an IR luminous quasar system. Comparing with star formation main sequence (MS) galaxies, at least 80 out of 207 quasars are hosted by starburst galaxies. It supports the statement that luminous AGNs are more likely to be associated with major mergers. The SFR increases with the redshift up to $z=2$. It is correlated with the AGN bolometric luminosity, where $L_{\rm FIR} \propto L_{\rm Bol}^{0.46\pm0.03}$. The AGN bolometric luminosity is also correlated with the host galaxy mass and gas mass. Yet the correlation between $L_{\rm FIR}$ and $L_{\rm Bol}$ has higher significant level, implies that the link between AGN accretion and the SFR is more primal. The $M_{\rm BH}/M_{\ast}$ ratio of our sample is 0.02, higher than the value 0.005 in the local Universe. It might indicate an evolutionary trend of the $M_{\rm BH} - M_{\ast}$ scaling relation.